1. Field of the Disclosure
The present application relates to an organic light emitting diode display, and more particularly to an organic light emitting diode display and a manufacturing method thereof that are adapted to enhance reliability by shielding it from external moisture and oxygen.
2. Description of the Related Art
Image display devices used for displaying a variety of information on a screen are one of the core technologies of the information and communication era. Such image display devices have been being developed to be thinner, lighter, and more portable, and furthermore to have a high performance. Actually, flat panel display devices are spotlighted in the display field due to their reduced weight and volume, well known disadvantages of cathode ray tubes (CRTs). The flat panel display devices include OLED (organic light-emitting display) devices which display images by controlling the light emitting quantity of an organic light emission layer. The OLED devices are self-illuminating display devices employing a thin light emission layer between electrodes. As such, the OLED devices can become thinner like a paper.
An ordinary OLED device is configured with a sub-pixel driver array and an organic light emitting element array which are formed on a substrate. The ordinary OLED device displays images by enabling light to be emitted from organic light emitting elements of the organic light emitting element array and to pass through the substrate or a barrier layer.
The organic light emitting element is easy to deteriorate due to internal and external factors. The internal factors include deterioration of the electrodes and the light emission layer caused by oxygen and deterioration of the light emission layer caused by interfacial reactions. The external factors include external moisture and oxygen, ultraviolet rays, manufacturing condition of the organic light emitting element and so on. Particularly, external oxygen and moisture greatly affect the lifespan of the organic light emitting element. As such, it is very important to package the organic light emitting element.
As a packaging method, a process of sealing a substrate, on which with the organic light emitting element is formed, using a protective cap is being used. In order to remove moisture within the protective cap, a moisture absorbent is attached to at a central portion the inside surface of the protective cap prior to sealing the substrate. Also, a semi-permeable film allowing for moisture and oxygen to come in and out must be attached to the inner surface of the protective cap, in order to prevent the fall of the moisture absorbent on an organic material layer of the organic light emitting element.
Such a packaging method allows the organic material layer of the organic light emitting element to be packaged with the protective cap, which is formed form glass or a metal, and protected from oxygen and moisture. However, the packaging method can increase manufacturing costs because of using additional material such as an adhesive and a moisture absorbent. Also, the protective cap can increase the volume and thickness of the OLED device. Moreover, it is difficult for a flexible OLED device to apply the packaging method, because the protective cap is formed from glass or a metal.
To address this matter, an encapsulation method has been proposed as a different method for packaging the OLED device. The encapsulation method forms a thin barrier layer on a substrate provided with the organic light emitting element, in order to package the OLED device. The barrier layer is formed to include either an inorganic film or the inorganic film and a polymer film stacked thereon.
However, the inorganic film requires a high deposition temperature and has an inferior coverage and a low density. Due to this, it is difficult to use the inorganic film as a protective film of the organic light emitting element.